This proposal describes the design and construction of a prototype instrument for cell selection and sorting. This device can be applied to cells in culture which are attached to a solid support and maintained under favorable conditions for growth. This environment will be sustained within a novel incubation chamber which provides flowing nutrient media and allows in situ analysis and sorting. The instrument utilizes a laser-illuminated fluorescence microscope system equipped with computer controlled beam attenuation and two-dimensional stage movement. A dedicated microcomputer directs the sorting operations and provides graphic/tabular output of the acquired data. The basis of cell selection is provided by fluorescent labelling of specific cellular components. Subsequent to labelling, the instrument will examine the entire area of the growth plate and select cells based upon differential responses. Sorting then proceeds by either isolating the desired cells and their underlying support by a laser inscribing action allowing physical separation, or by sparing the desired cells from a high-intensity laser beam which destroys all other cells. Since most normal cell lines exhibit anchorage-dependent mechanisms to maintain cell function and differentiation, this development advances the art of cell sorting to include all types of cultured cells.